North American Turbocoupe Organization



any way to test the computer
powerhouse Offline
Junior Member
#1
I was trying to read the codes on the 86 t/c I just bought by the procedure shown in the tech articles here first using a test lite then a voltmeter. I was unable to get any reading.After doing this I attempted to start the car and it wouldn't start. I discovered there was no spark. I swapped the tfi and coil for known good peices. With the key in the run position I have power at the coil and at the white/blue wire on the distributor plug. There is also power after the fusable link for the computer main power feed that is attached to the solenoid. I am stumped. Car ran fine before I did this. Any thoughts or suggestions are appreciated. Thanks Andy
88 t/c
85 mustang gt 351w
81 capri 306
Powerhouse Performance Machine - race/performance engines
508-328-9884
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Jeff K Offline
Administrator
#2
Be sure the PCM is powered up. Easiest way to do this, since you dont have a CEL, is to see if you have 5V VREF at either the TPS or VAM connectors. If PCM is powered up, be sure the orange ground wire at the turbo inlet is connected and tight. PCM wont output codes if this is disconnected.

Coil and TFI are powered seperately from PCM. so power there doesnt mean anything.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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powerhouse Offline
Junior Member
#3
Ok thanks. I will check this though it probably won't be until Monday. The ground wire is connected fimly on the turbo, I already checked this. Thanks
88 t/c
85 mustang gt 351w
81 capri 306
Powerhouse Performance Machine - race/performance engines
508-328-9884
Reply

rs1sensen Offline
Member
#4
Jeff has a good point on checking the 5V VREF signal. When my VAM went out, it essentially grounded the circuit off the computer. This meant my car did not start, and, it would not throw me any codes.

Have you checked to see if your fuel pump is priming when you turn the key to run?

I picked up a code reader for the car at autozone some time back, and then got sick of counting flashes so I picked up this one, which actually shows the code: http://www.amazon.com/Equus-3145-Ford-Di...B000EW0KHW

It might be worth your while to invest in one at some point. I've found that doing the test light technique is a bit of a minor pain, and with a 25 year old car, you might find yourself reading codes often. (at least, I have!)
1985 Thunderbird Turbo Coupe w/ Approx 75k miles
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powerhouse Offline
Junior Member
#5
Yes the fuel pump primes. I think the injectors are working to because when I pulled the plugs after it wouldn't start the were wet with gas. I'm just afraid that when I was trying to get the codes I somehow damaged something in the computer. I will report back after I check for power at the tps and vam.
88 t/c
85 mustang gt 351w
81 capri 306
Powerhouse Performance Machine - race/performance engines
508-328-9884
Reply

Jeff K Offline
Administrator
#6
If you have no spark, that has nothing to do with the computer. If the PCM is completely removed from the car but the TFI and PIP are powered up and working as well as the coil, you will still get spark at the base timing (no advance retard), but, of cource, the car wont start.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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powerhouse Offline
Junior Member
#7
Ok so I got a chance to check a few things today. I do have 5 volts at both the tps and vam. Fuel pump primes and injectors definately work as the plugs were again soaked with fuel after cranking. Still no spark though.
88 t/c
85 mustang gt 351w
81 capri 306
Powerhouse Performance Machine - race/performance engines
508-328-9884
Reply

powerhouse Offline
Junior Member
#8
Is it possible some of the electronics in the distributor got damaged ? I swapped a known good tfi and coil and still no spark. I was told on another forum to check if I had a pulse at the coil neg. Wire. I checked this with a testlite and a volt meter with no pulse being shown on either. Is a distributor from an 88 the same ? I can swap the distributor out to a known good one to see if that works. Thanks again for the help and suggestions. Andy
88 t/c
85 mustang gt 351w
81 capri 306
Powerhouse Performance Machine - race/performance engines
508-328-9884
Reply

Robert Camp Offline
Posting Freak
#9
The distributors are the same. Do you have 12v at the coil. The TFI is totally responsible for control of the coil. It grounds the coil primary to energizes the coil and opens the circuit to fire the plug. The EEC sends a signal, SPOUT, used by the TFI to modify the timing only.
So if you've got 12 v to the coil and no TFI control on the ground side of coil primary, then there's no spark. Or if the coil is shorted or open. Concentrate on the TFI, distributor, PIP and coil.
Robert Camp
'86 Medium Regatta Blue TC, 5-speed, original owner.
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powerhouse Offline
Junior Member
#10
Ok that makes sense. I do have 12v at the coil and the tfi is a known good peice as is the coil. My next step will be to ensure the distributor is functioning properly....no sheared roll pin...to ensure the rotor is spinning......if that checks ok I will swap distributors to a known good peice to see what happens. Thanks. Andy
88 t/c
85 mustang gt 351w
81 capri 306
Powerhouse Performance Machine - race/performance engines
508-328-9884
Reply





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